Case #484 – January, 2019

A 36-year-old man, who has made 2-3 trips per year for the past 5 years to various countries in Africa, sought medical attention for a recent episode of angioedema of the face and arms. He reported being bitten by insects on most trips, but on a recent trip he confessed to not taking any recommended malaria prophylaxis. A blood smear was ordered mid-day, prepared and stained with Giemsa. Two objects of interest were detected on a thin smear. Figures A and B shows one object at 500x and 1000x oil immersion respectively; the other object is shown in Figure C at 500x and Figures D and E at 1000x oil immersion.

What is your diagnosis? Based on what criteria?

Figure A

Figure D

Figure B

Figure E

Figure C

This was a case of loiasis caused by Loa loa, a filarid referred to as the African eye worm. Diagnostic morphologic features shown included:

Presence of microfilariae in blood collected during the day
Robust microfilariae with a short head space and a tapered tail with nuclei spaced irregularly to the tip of the tail (Figures B and E)
Evidence of a sheath that did not stain with Giemsa

More on loiasis: https://www.cdc.gov/dpdx/loiasis/index.html

Images presented in the dpdx case studies are from specimens submitted for diagnosis or archiving. On rare occasions, clinical histories given may be partly fictitious.